“3D printing of nanowire based sensors in non-planar heterojunction network” – is the new exceptional scientific paper signed by the professors of the Department of Microelectronics and Biomedical Engineering (DMIB) from the Faculty of Computers, Informatics and Microelectronics, Nicolai ABABII, PhD, third year, Grant of Excellence of the Government of the Republic of Moldova, university lecturer, together with prof., PhD Victor ȘONTEA, head of DMIB, and prof. Oleg LUPAN, director of the Center for Nanotechnologies and Nanosensors, DMIB. In collaboration with the team of Professor Rainer ADELUNG, dr. at the University of Kiel, Germany, our researchers have designed, obtained and researched for the first time nanowire acetone sensors in the p-n heterojunction network using the 3D printing method (https://authors.elsevier.com/c/1aRAp7soS7u27~). The results of this scientific work were reviewed, accepted and published quickly in one of the prestigious scientific journals – “Nano Energy” (Elsevier) with impact factor 15.5, by the editor-in-chief, prof., Dr. Zhong Lin WANG, with the index h of over 200 (SCOPUS) ranked #15 worldwide among all scientists in all fields! (https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000384)
Increased demand for individual devices in the modern Internet-of-Things (IoT) era with selected sets of properties, clearly defined by the consumer, requires sophisticated multi-purpose materials, but also modern technological approaches to fabricate devices from these nanomaterials.
In this work, a facile two-step fabrication and characterization of printed acetone sensors based on mixed semiconducting metal oxides (type-p and type-n) is introduced. The devices are fabricated by Direct Ink Writing metal microparticle (MP) stripes of commercially available pure iron and copper particles onto the surface of a glass substrate, forming a bridging multi-phase semiconducting oxide net by subsequent thermal annealing. The 3D structure proposed and elaborated by the authors is open, highly porous bridging structures consist of heterojunctions which are interconnected via non-planar CuO/Cu2O/Cu nanowires and Fe2O3/Fe nanospikes. Morphological, vibrational, chemical and structural studies were performed to investigate the contact-forming Fe2O3–CuO nanostructures on the surface of the MPs. At the same time, the authors concentrate on the study of power consumption and the gas sensing properties showed selectivity to acetone vapor at an operating temperature of around 300 °C with a high gas response of about 50% and the lowest operating power of around 0.26 μW to a concentration of 100 ppm of acetone vapor. The combination of the possibility of acetone vapor detection, the controllable size and geometry and their low power make these printed structures important candidates for next developments of accessible detection devices, as well as acetone vapor monitoring (even below 1 ppm). The printing of MPs in general paves the way for a new generation of printed different devices, even in “home-made” conditions, for a manifold of applications tailored by the composition and geometry of the printed MP stripes, enabled through the simplicity and versatility of the fabrication method. [1-3]
Acetone vapors are a reagent widely used in households, industry and various laboratory applications. It is very harmful to human health and biology, so its rapid identification is crucial [4-7]. Historically, endogenous acetone is measured in exhaled breath to monitor ketosis in healthy and diabetic patients. The level of these breath acetone can vary from 1 ppm in healthy people and at more than 2 ppm – 1250 ppm in patients with diabetic ketoacidosis . Thus, 3D printed individual portable devices for such sensors are very important to be produced in a large and cost effective way, as the number of diabetics has increased significantly (doubled) in the last decades.
The importance of the elaboration (https://authors.elsevier.com/c/1aRAp7soS7u27~) consists in the simplicity of the 3D printed device on the basis of the mixed semiconductors of metal oxides (type-p and type-n), junction formation at the nanometric scale and the possibility of expansion in production with microelectronic, electronic and biomedical applications without using sophisticated laboratories or “clean rooms” and sophisticated – costly technological processes. In this way, these results obtained by the professors of the MIB department, FCIM, UTM, in collaboration with the scientists from Germany, represent an important step in the field of nanoscience, microelectronics, cost-effective nanotechnologies, but also of nano-engineering internationally.
The internationally reported and appreciated research was supported in part by the NATO Science for Peace and Security Program (SPS) project grant G5634, AMOXES “Advanced Electro-Optical Chemical Sensors” and by UTM.
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 O. Lupan, V. Postica, N. Wolff, O. Polonskyi, V. Duppel, V. Kaidas, E. Lazari, N. Ababii, F. Faupel, L. Kienle, R. Adelung, Localized synthesis of iron oxide nanowires and fabrication of high performance nanosensors based on a single Fe2O3 nanowire, Small 13 (2017) 1602868, https://doi.org/10.1002/ smll.201602868
 Nano Energy 70 (2020) 104420